gb: Add beginnings of a new BSSGP implementation

Similar to ns2 superseding ns, we now also intoduce a next generation
of BSSGP related code to libosmogb.  However, this is not aiming to
be a full implementation yet, but simply those parts that we currently
need from the revamped osmo-gbproxy.

The gprs_bssgp2.[ch] differs in two ways from the old code:
* it separates message encoding from message transmission
* it supports more recent specs / IEs

bssgp_bvc_fsm.c is a genric implementation of the BSSGP BVC
RESET/BLOCK/UNBLOCK logic with support for both PTP and signaling,
both on the SGSN side and the BSS side.

Change-Id: Icbe8e4f03b68fd73b8eae95f6f6cccd4fa9af95a

1 files changed, 240 insertions, 0 deletions

diff --git a/src/gb/gprs_bssgp2.c b/src/gb/gprs_bssgp2.c
new file mode 100644
index 00000000..e741fb46
--- /dev/null
+++ b/src/gb/gprs_bssgp2.c
@@ -0,0 +1,240 @@
+/* BSSGP2 - second generation of BSSGP library */
+
+/* (C) 2020 Harald Welte <laforge@gnumonks.org>
+ *
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/byteswap.h>
+#include <osmocom/core/msgb.h>
+
+#include <osmocom/gsm/gsm48.h>
+#include <osmocom/gsm/tlv.h>
+
+#include <osmocom/gprs/gprs_ns2.h>
+#include <osmocom/gprs/gprs_bssgp.h>
+#include <osmocom/gprs/gprs_bssgp2.h>
+
+
+/*! transmit BSSGP PDU over NS (PTP BVC)
+ *  \param[in] nsi NS Instance through which to transmit
+ *  \param[in] nsei NSEI of NSE through which to transmit
+ *  \param[in] bvci BVCI through which to transmit
+ *  \param[in] msg BSSGP PDU to transmit
+ *  \returns 0 on success; negative on error */
+int bssgp2_nsi_tx_ptp(struct gprs_ns2_inst *nsi, uint16_t nsei, uint16_t bvci,
+		      struct msgb *msg, uint32_t lsp)
+{
+	struct osmo_gprs_ns2_prim nsp = {};
+	int rc;
+
+	if (!msg)
+		return 0;
+
+	nsp.bvci = bvci;
+	nsp.nsei = nsei;
+	nsp.u.unitdata.link_selector = lsp;
+
+	osmo_prim_init(&nsp.oph, SAP_NS, PRIM_NS_UNIT_DATA, PRIM_OP_REQUEST, msg);
+	rc = gprs_ns2_recv_prim(nsi, &nsp.oph);
+
+	return rc;
+}
+
+/*! transmit BSSGP PDU over NS (SIGNALING BVC)
+ *  \param[in] nsi NS Instance through which to transmit
+ *  \param[in] nsei NSEI of NSE through which to transmit
+ *  \param[in] msg BSSGP PDU to transmit
+ *  \returns 0 on success; negative on error */
+int bssgp2_nsi_tx_sig(struct gprs_ns2_inst *nsi, uint16_t nsei, struct msgb *msg, uint32_t lsp)
+{
+	return bssgp2_nsi_tx_ptp(nsi, nsei, 0, msg, lsp);
+}
+
+/*! Encode BSSGP BVC-BLOCK PDU as per TS 48.018 Section 10.4.8. */
+struct msgb *bssgp2_enc_bvc_block(uint16_t bvci, enum gprs_bssgp_cause cause)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+	uint16_t _bvci = osmo_htons(bvci);
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_BVC_BLOCK;
+
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+	msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, (uint8_t *) &cause);
+
+	return msg;
+}
+
+/*! Encode BSSGP BVC-BLOCK-ACK PDU as per TS 48.018 Section 10.4.9. */
+struct msgb *bssgp2_enc_bvc_block_ack(uint16_t bvci)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+	uint16_t _bvci = osmo_htons(bvci);
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_BVC_BLOCK_ACK;
+
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+
+	return msg;
+}
+
+/*! Encode BSSGP BVC-UNBLOCK PDU as per TS 48.018 Section 10.4.10. */
+struct msgb *bssgp2_enc_bvc_unblock(uint16_t bvci)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+	uint16_t _bvci = osmo_htons(bvci);
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_BVC_UNBLOCK;
+
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+
+	return msg;
+}
+
+/*! Encode BSSGP BVC-UNBLOCK-ACK PDU as per TS 48.018 Section 10.4.11. */
+struct msgb *bssgp2_enc_bvc_unblock_ack(uint16_t bvci)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+	uint16_t _bvci = osmo_htons(bvci);
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_BVC_UNBLOCK_ACK;
+
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+
+	return msg;
+}
+
+/*! Encode BSSGP BVC-RESET PDU as per TS 48.018 Section 10.4.12.
+ *  \param[in] bvci PTP BVCI to encode into the BVCI IE
+ *  \param[in] cause BSSGP Cause value (reason for reset)
+ *  \param[in] ra_id Routing Area ID to be encoded to CELL_ID IE (optional)
+ *  \param[in] cell_id Cell ID to be encoded to CELL_ID IE (only if ra_id is non-NULL)
+ *  \param[in] feat_bm Feature Bitmap (optional)
+ *  \param[in] ext_feat_bm Extended Feature Bitmap (optional) */
+struct msgb *bssgp2_enc_bvc_reset(uint16_t bvci, enum gprs_bssgp_cause cause,
+				  const struct gprs_ra_id *ra_id, uint16_t cell_id,
+				  const uint8_t *feat_bm, const uint8_t *ext_feat_bm)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+	uint16_t _bvci = osmo_htons(bvci);
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_BVC_RESET;
+
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+	msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, (uint8_t *) &cause);
+	if (ra_id) {
+		uint8_t bssgp_cid[8];
+		bssgp_create_cell_id(bssgp_cid, ra_id, cell_id);
+		msgb_tvlv_put(msg, BSSGP_IE_CELL_ID, sizeof(bssgp_cid), bssgp_cid);
+	}
+
+	if (feat_bm)
+		msgb_tvlv_put(msg, BSSGP_IE_FEATURE_BITMAP, 1, feat_bm);
+
+	if (ext_feat_bm)
+		msgb_tvlv_put(msg, BSSGP_IE_EXT_FEATURE_BITMAP, 1, feat_bm);
+
+	return msg;
+}
+
+/*! Encode BSSGP BVC-RESET-ACK PDU as per TS 48.018 Section 10.4.13.
+ *  \param[in] bvci PTP BVCI to encode into the BVCI IE
+ *  \param[in] ra_id Routing Area ID to be encoded to CELL_ID IE (optional)
+ *  \param[in] cell_id Cell ID to be encoded to CELL_ID IE (only if ra_id is non-NULL)
+ *  \param[in] feat_bm Feature Bitmap (optional)
+ *  \param[in] ext_feat_bm Extended Feature Bitmap (optional) */
+struct msgb *bssgp2_enc_bvc_reset_ack(uint16_t bvci, const struct gprs_ra_id *ra_id, uint16_t cell_id,
+				      const uint8_t *feat_bm, const uint8_t *ext_feat_bm)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+	uint16_t _bvci = osmo_htons(bvci);
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_BVC_RESET_ACK;
+
+	msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+	if (ra_id) {
+		uint8_t bssgp_cid[8];
+		bssgp_create_cell_id(bssgp_cid, ra_id, cell_id);
+		msgb_tvlv_put(msg, BSSGP_IE_CELL_ID, sizeof(bssgp_cid), bssgp_cid);
+	}
+
+	if (feat_bm)
+		msgb_tvlv_put(msg, BSSGP_IE_FEATURE_BITMAP, 1, feat_bm);
+
+	if (ext_feat_bm)
+		msgb_tvlv_put(msg, BSSGP_IE_EXT_FEATURE_BITMAP, 1, feat_bm);
+
+	return msg;
+}
+
+/*! Encode BSSGP STATUS PDU as per TS 48.018 Section 10.4.14.
+ *  \param[in] cause BSSGP Cause value
+ *  \param[in] bvci optional BVCI - only encoded if non-NULL
+ *  \param[in] msg optional message buffer containing PDU in error - only encoded if non-NULL */
+struct msgb *bssgp2_enc_status(uint8_t cause, const uint16_t *bvci, const struct msgb *orig_msg)
+{
+	struct msgb *msg = bssgp_msgb_alloc();
+	struct bssgp_normal_hdr *bgph;
+
+	if (!msg)
+		return NULL;
+
+	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
+	bgph->pdu_type = BSSGP_PDUT_STATUS;
+	msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, &cause);
+	if (bvci) {
+		uint16_t _bvci = osmo_htons(*bvci);
+		msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
+	}
+	if (orig_msg)
+		msgb_tvlv_put(msg, BSSGP_IE_PDU_IN_ERROR, msgb_bssgp_len(orig_msg), msgb_bssgph(orig_msg));
+
+	return msg;
+}